Battery systems with embedded cell monitors

ABSTRACT

A battery pack is disclosed. The battery pack includes a battery cell and a cell monitor. The cell monitor is embedded in the battery cell and is operable for monitoring the battery cell and for generating an alert signal indicative of a predetermined condition of the battery cell.

RELATED APPLICATION

This application claims priority to U.S. Provisional Application No.60/872,077, titled Embedded Battery Cell Monitor, filed on Dec. 1, 2006,which is hereby incorporated by reference in its entirety.

BACKGROUND

1. Field of the Invention

The present invention relates to power systems and more particularly tobattery systems with embedded cell monitors.

2. Description of the Related Art

Batteries are widely used in electronic devices for providing power toelectronic devices, such as notebook computers, mobile phones, etc.However, temperature of a battery can rise when the battery is incharging or discharging. Lithium-ion batteries, especially cobaltcathode chemistry type batteries can reach a critical temperature (e.g.,between 135 degrees Celsius and 145 degrees Celsius) when exothermicreaction becomes self-sustaining. High temperature can deterioratebatteries.

In a conventional electronic system, a thermistor can be employed tomonitor a temperature of the battery pack. However, the thermistorcannot respond quickly to a high temperature of a battery cell that islocated far from the thermistor.

SUMMARY OF THE INVENTION

A battery pack is disclosed herein. The battery pack includes a batterycell and a cell monitor. The cell monitor is embedded in the batterycell and is operable for monitoring the battery cell and for generatingan alert signal indicative of a predetermined condition of the batterycell.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantages of the present invention will be apparent from the followingdetailed description of exemplary embodiments thereof, which descriptionshould be considered in conjunction with the accompanying drawings, inwhich:

FIG. 1 illustrates a block diagram of a battery cell with an embeddedcell monitor, in accordance with one embodiment of the presentinvention.

FIG. 2A illustrates a diagram of a battery cell with an embedded cellmonitor, in accordance with one embodiment of the present invention.

FIG. 2B illustrates a diagram of a battery cell with an embedded cellmonitor, in accordance with one embodiment of the present invention.

FIG. 3 illustrates a block diagram of a battery system, in accordancewith one embodiment of the present invention.

FIG. 4 illustrates a block diagram of a battery system, in accordancewith one embodiment of the present invention.

FIG. 5 illustrates a cross-section diagram of a die of an embedded cellmonitor, in accordance with one embodiment of the present invention.

FIG. 6 illustrates a cross-section diagram of a die of an embedded cellmonitor, in accordance with one embodiment of the present invention.

FIG. 7 illustrates a die of an embedded cell monitor, in accordance withone embodiment of the present invention.

FIG. 8 illustrates a block diagram of an electronic system, inaccordance with one embodiment of the present invention.

FIG. 9 illustrates a flowchart of operations performed by a batterysystem, in accordance with one embodiment of the present invention.

DETAILED DESCRIPTION

Battery packs/systems with embedded cell monitors are disclosed hereinin the present disclosure. Since embodiments shown in the drawings arefor illustrative purposes, some sub-components and/or peripheralcomponents generally incorporated in the disclosure are omitted hereinfor brevity and clarity. In describing embodiments in accordance withthe present invention, specific terminologies are employed for the sakeof clarity. However, the disclosure of this patent specification is notintended to be limited to selected terminologies and specifiedembodiments. It is understood that each specific element includes alltechnical equivalents that operate in a similar manner.

In one embodiment, a battery pack including one or more battery cells isprovided. A cell monitor is embedded in each battery cell and isoperable for monitoring a corresponding battery cell and for generatingan alert signal indicative of a predetermined condition (e.g., anundesirable condition, or a fault condition) of the correspondingbattery cell. Each cell monitor includes a sensing circuit operable fordetecting the predetermined condition of the corresponding battery celland for generating a detecting signal. Each cell monitor furtherincludes a transmitter operable for generating the alert signalaccording to the detecting signal of the cell monitor. The battery packfurther includes a receiver for receiving the alert signal and includesa battery management unit for triggering a protection action (e.g.,terminating battery pack charging or terminating battery packdischarging) for the battery pack according to the alert signal.

FIG. 1 illustrates a block diagram of a battery cell 100 with anembedded cell monitor 101, in accordance with one embodiment of thepresent invention. The battery cell 100 is in a battery pack (not shownin FIG. 1 for purposes of brevity and clarity). The cell monitor 101 isembedded in the battery cell 100 and is coupled between a positiveterminal 131 and a negative terminal 133 of the battery cell 100. Thecell monitor 101 is operable for monitoring the battery cell 100 and forgenerating an alert signal 191 indicative of a predetermined condition(e.g., an undesirable condition) of the battery cell 100. In oneembodiment, the undesirable condition can include, but is not limitedto, an over-voltage condition and an over-temperature condition. In oneembodiment, the cell monitor 101 includes a sensing circuit 104 operablefor detecting an undesirable condition of the battery cell 100 and forgenerating a detecting signal 103 indicative of the detected undesirablecondition. The cell monitor 101 further includes a transmitter 135operable for receiving the detecting signal 103 and for generating thealert signal 191 according to the detecting signal 103 from the sensingcircuit 104. Advantageously, the battery pack can obtain the alertsignal 191 and perform a corresponding protection action (e.g.,terminating battery pack charging or terminating battery packdischarging) to protect the battery pack from being deteriorated in theundesirable condition.

FIG. 2A illustrates a detailed diagram of a battery cell 100A with anembedded cell monitor 101, in accordance with one embodiment of thepresent invention. Elements that are labeled the same as in FIG. 1 havesimilar functions and hence any repetitive description of these elementsis omitted herein for purposes of clarity and brevity. In oneembodiment, the sensing circuit 104 is operable for detecting anundesirable condition of the battery cell 100A and for generating adetecting signal 103. The transmitter 135A is operable for generating analert signal 191 according to the detecting signal 103 from the sensingcircuit 104.

More specifically, the sensing circuit 104 can include a voltage sensor111, a comparator 117, and a logic OR gate 121. In one embodiment, thevoltage sensor 111 can be a resistor. The voltage sensor 111 is operablefor monitoring a voltage of the battery cell 100A. The voltage monitoredby the voltage sensor 111 is compared with a reference voltage 113 bythe comparator 117. The reference voltage 113 can be a predeterminedthreshold voltage. If the voltage of the battery cell 100A is greaterthan the reference voltage 113, which may indicate an over-voltagecondition, the comparator 117 generates a signal (e.g., with a highvoltage level) to the logic OR gate 121.

In one embodiment, the sensing circuit 104 also includes a temperaturesensor 115 and a comparator 119. In one embodiment, the temperaturesensor 115 can be a thermistor. The temperature sensor 115 is operablefor monitoring a temperature of the battery cell 100A and for generatinga signal indicative of the temperature of the battery cell 100A. Thesignal indicative of the temperature of the battery cell 100A has avoltage level Vt. The voltage level Vt is compared with the referencevoltage 113 by the comparator 119. If the voltage level Vt is greaterthan the reference voltage 113, which may indicate an over-temperaturecondition, the comparator 119 generates a signal (e.g., with a highvoltage level) to the logic OR gate 121.

In one embodiment, the voltage sensor 111 and the temperature sensor 115continuously monitor the voltage and the temperature of the battery cell100A respectively. If an undesirable condition (e.g., an over-voltagecondition and/or an over-temperature condition) occurs, the logic ORgate 121 can generate a detecting signal 103 (e.g., with a high voltagelevel) to the transmitter 135A. The transmitter 135A can generate analert signal 191 to the battery pack according to the detecting signal103 if the undesirable condition occurs. More specifically, if thevoltage of the battery cell 100A is greater than a predeterminedthreshold and/or if the temperature of the battery cell 100A is greaterthan a predetermined threshold, the alert signal 191 will be generated.Consequently, corresponding actions can be performed to protect thebattery pack.

In one embodiment, the transmitter 135A includes a pulse generator 105,a resistor 109, and a switch 107 (e.g., a transistor) coupled to thepulse generator 105. When the pulse generator 105 receives the detectingsignal 103 indicative of the undesirable condition, the pulse generator105 can generate a series of pulses to the switch 107 according to thedetecting signal 103. In one embodiment, the pulse generator 105 cangenerate a series of high current pulses with a frequency f0 (e.g., apulse width modulation signal with a duty cycle of 1%) in response tothe detecting signal 103. The switch 107 is operable for receiving theseries of pulses from the pulse generator 105 and for generating thealert signal 191. In one embodiment, the switch 107 is switched on andoff periodically by the pulses. Thus, the alert signal 191 is shown asan AC signal having a frequency f0, in one embodiment. The cell voltageof the battery cell 100A drops when the switch 107 is on. Consequently,the cell voltage between terminals 131 and 133 can be shown as an ACvoltage with the frequency f0 in response to the alert signal 191, inone embodiment.

FIG. 2B illustrates another detailed diagram of a battery cell 100B withan embedded cell monitor 101, in accordance with one embodiment of thepresent invention. Elements that are labeled the same as in FIG. 1 andFIG. 1A have similar functions and will not be repetitively describedherein for purposes of clarity and brevity. In one embodiment, the cellmonitor 101 includes a transmitter 135B for receiving the detectionsignal 103 and for generating the alert signal 191 according to thedetection signal 103. More specifically, the transmitter 135B includesan oscillator 205 and a capacitor 207 coupled to the oscillator 205, inone embodiment. In one embodiment, the oscillator 205 can be a radiofrequency signal tone oscillator. In another embodiment, the oscillator205 can be a radio frequency dual tone oscillator.

The oscillator 205 can receive the detecting signal 103 from the logicOR gate 121. In one embodiment, the oscillator 205 has a frequency foscand generates an oscillation signal, e.g., a sinusoidal AC waveformhaving a high frequency fosc (e.g., 10 MHz), as the alert signal 191according to the detecting signal 103. The capacitor 207 is operable fortransferring the alert signal 191 having the frequency fosc to thebattery cell 100B. As a result, when the voltage sensor 111 detects anover-voltage condition, and/or the temperature sensor 115 detects anover-temperature condition, the cell voltage of the battery cell 100Bcan be shown as an AC voltage with the frequency fosc in response to thealert signal 191.

As discussed above in relation to FIG. 2A and FIG. 2B, the alert signal191 can reflect an undesirable condition of the battery cell 100, e.g.,an over-temperature and/or an over-voltage condition. Consequently, anAC voltage can be shown across the battery cell in response to the alertsignal 191. Description will now be made with reference to FIG. 3 withrespect to detecting such alert signal and performing correspondingactions if an undesirable condition occurs.

FIG. 3 shows a block diagram of a battery system 300 (e.g., a batterypack), in accordance with one embodiment of the present invention. Thebattery pack 300 includes one or more battery cells 310 coupled inseries or in parallel, each of which can employ the configuration inFIG. 1, in one embodiment. A cell monitor is embedded in each of thebattery cells 310. Therefore, battery cells 310 are monitored byembedded cell monitors individually and respectively. The battery pack300 further includes a positive terminal 331, a negative terminal 333, areceiver 301, a battery management unit 305, and a switch 307 controlledby the battery management unit 305, in one embodiment. As describedabove in relation to FIG. 2A and FIG. 2B, when an undesirable condition(e.g., an over-temperature condition and/or an over-voltage condition)is detected in a battery cell, an AC voltage can be shown across thebattery cell in response to the alert signal. Thus, an AC voltage can beshown between the positive terminal 331 and the negative terminal 333 ofthe battery pack 300, in one embodiment. The receiver 301 is coupled tothe positive terminal 331 and the negative terminal 333 of the batterypack 300 and is operable for receiving the alert signal from a cellmonitor by detecting an AC voltage between the positive terminal 331 andthe negative terminal 333 of the battery pack 300, in one embodiment.The receiver 301 can also generate a driving signal 303 according to thealert signal.

In one embodiment, the receiver 301 includes a high pass filter shown asa capacitor 313 and a resistor 315 coupled in series for filteringnoises associated with the battery pack 300. In one embodiment, if thealert signal (e.g., an AC signal) from battery cells 310 has thefrequency f0 higher than a cutoff frequency of the high-pass filter, thereceiver 301 can generate a driving signal 303. The battery managementunit 305 can receive the driving signal 303 from the receiver 301 andgenerate a switching signal 391 according to the driving signal 303.Corresponding actions can be performed to protect the battery pack 300in response to the switching signal 391. For example, the switchingsignal 391 turns off the switch 307 to terminate batterycharging/discharging in order to protect the battery pack 300 fromdeterioration.

In one embodiment, the battery management unit 305 includes a detectioncircuit 340 for detecting the driving signal 303 from the receiver 301.Such configuration is for illustrative purpose and other configurationscan also be employed in the battery management unit 305. The detectioncircuit 340 includes a rectifier 341 and a comparator 345, in oneembodiment. The rectifier 341 can be a high frequency rectifier forreceiving the driving signal 303 and for rectifying the driving signal303. In one embodiment, the rectifier 341 generates a voltage signalaccording to the driving signal 303. Then the comparator 345 comparesthe voltage signal with a reference signal 343. If the voltage level ofthe voltage signal from the rectifier 341 is greater than the voltagelevel of the reference signal 343, the comparator 345 outputs a signal(e.g., with a high voltage level) to the battery management unit 305, inone embodiment. Then the battery management unit 305 can generate aswitching signal 391 according to a result of the comparison to triggera protection action for the battery pack 300. For example, the switchingsignal 391 can turn off the switch 307, which is coupled to the positiveterminal 331 of the battery pack 300. Consequently, the battery pack 300can be disconnected from a load or a charger (not shown in FIG. 3 forpurposes of brevity and clarity) and can be protected from beingdeteriorated in the over-temperature condition and/or over-voltagecondition.

FIG. 4 illustrates a block diagram of a battery system 400 (e.g., abattery pack), in accordance with another embodiment of the presentinvention. Elements that are labeled the same as in FIG.3 have similarfunctions and will not be repetitively described herein for purposes ofclarity and brevity. The battery pack 400 includes a receiver 401similar to the receiver 301 in FIG. 3. The receiver 401 detects thealert signal from battery cells 310 and generates a driving signal 303to the battery management unit 305. In one embodiment, the receiver 401includes a band-pass filter shown as a capacitor 313, an inductor 417and a resistor 315 in series for filtering noises associated with thebattery pack 400. In one embodiment, a resonant frequency of theband-pass filter can be set to be equal to the frequency of the alertsignal 191 in FIG. 2A and FIG. 2B. Therefore, the alert signal can passthrough the band-pass filter. Thus, the receiver 401 can receive thehigh frequency alert signal from battery cells 310 and generate thedriving signal 303. The battery management unit 305 can generate aswitching signal 391 according to the driving signal 303. The switchingsignal 391 can trigger a protection action for the battery pack 400 bycontrolling the switch 307. For example, the switch 307 can be turnedoff by the switching signal 391 under the control of the batterymanagement unit 305. Consequently, the battery pack 400 can bedisconnected from a load or a charger (not shown in FIG. 4 for purposesof brevity and clarity) and can be protected from being deteriorated inundesirable conditions.

Accordingly, when a predetermined condition (e.g., an over-temperaturecondition and/or an over-voltage condition) is detected by a cellmonitor 101 embedded in a battery cell 100 from battery cells 310, thecell monitor 101 can generate an alert signal. The alert signal cancause an AC voltage across the battery cell 100, in one embodiment.Therefore, an AC voltage can be shown between the positive terminal 331and the negative terminal 333 of the battery pack 300 (400) in responseto the alert signal. Then the receiver 301(401) can detect the alertsignal and generate the driving signal 303 to the battery managementunit 305. The battery management unit 305 can generate a switchingsignal 391 which can control the switch 307. The switch 307 is turnedoff under control of battery management unit 305 to protect the batterypack 300 (400) according to the driving signal 303. Advantageously, eachcell in battery cells 310 is monitored by an individual embedded cellmonitor. If one of the battery cells 310 is undergoing anover-temperature and/or over-voltage condition, the cell monitor in thatbattery cell can transmit an alert signal to alert the battery pack 300(400). Consequently, corresponding actions can be performed to protectthe battery pack 300 (400) from being deteriorated in undesirableconditions.

As described in FIG. 2B, the transmitter 135B includes the capacitor 207for transferring the alert signal from the oscillator 205 to thepositive terminal 131 of the battery cell 100B. The followingdescription made with reference to FIG. 5 and FIG. 6 describes anexemplary implementation of such capacitor in fabrication process.

FIG. 5 shows a cross-section diagram of a die 500, in which a cellmonitor (e.g., the cell monitor 101 in FIG. 2B) is fabricated, inaccordance with one embodiment of the present invention. Referring toFIG. 5, the die 500 includes a metal layer 503, a metal layer 505, andan insulator 507. The metal layer 503 and the metal layer 505 areinsulated by the insulator 507. A circuit 501 including the sensingcircuit 104 and the oscillator 205 in FIG. 2B is coupled to the metallayer 503 and the metal layer 505. During fabrication of the die 500,the metal layer 503 and the metal layer 505 are formed when fabricatingthe sensing circuit 104 and the oscillator 205. Advantageously, theinsulator 507 can be formed between the metal layer 503 and the metallayer 507, and thus the metal layer 503, the insulator 507 and the metallayer 505 can constitute the capacitor 207 with a relatively largecapacitance. Therefore, this configuration can avoid the formation oftwo extra metal layers for the purpose of the capacitor fabrication andthe cost of the die 500 can be decreased.

FIG. 6 shows another cross-section diagram of a die 600, in which thecell monitor 101 is fabricated, in accordance with one embodiment of thepresent invention. The die 600 includes multiple metal layers, e.g., ametal layer 603, a metal layer 605, and a metal layer 607. Metal layersare separated by an insulator 615 and an insulator 617. In oneembodiment, the metal layer 603 is coupled to the metal layer 607through a via 613. In one embodiment, a circuit 601 including thesensing circuit 104 and the oscillator 205 in FIG. 2B is coupled to themetal layer 605 and the metal layer 607. During fabrication of the die600, the metal layer 603, the metal layer 605, and the metal layer 607are formed when fabricating the sensing circuit 104 and the oscillator205. Advantageously, multiple metal layers can extend the number ofvertical layers of capacitors that can be provided. Therefore, the metallayer 603, the metal layer 605 and the insulator 615 can constitute afirst capacitor, the metal layer 605, the metal layer 607 and theinsulator 617 can constitute a second capacitor. The first capacitor andthe second capacitor are coupled in parallel as shown in FIG. 6.Advantageously, the capacitor 207 can include the first capacitor andsecond capacitor in parallel. Thus, the capacitance of the parallelconnected capacitors in FIG. 6 can be twice as the capacitance of thecapacitor in FIG. 5. In one embodiment, extra metal layers are saved toform the capacitor configuration and the cost of the die 600 can bereduced.

FIG. 7 illustrates a cell monitor die 700 of the cell monitor 101, inaccordance with one embodiment of the present invention. In oneembodiment, the cell monitor 101 is fabricated on the cell monitor die700. The cell monitor die 700 includes a bottom 705 (e.g., a substrate)and a top 703 (e.g., metal layer 503 in FIG. 5 or metal layer 603 inFIG. 6). Because the bottom 705 is ground, the bottom 705 can be coupledto the negative terminal of the battery cell 100, in one embodiment. Thetop 703 is a positive contact, which can be coupled to the positiveterminal 131 of the battery cell 100 by a single wire, in oneembodiment. Therefore, a single wire can embed the cell monitor die intothe battery cell 100. Advantageously, the cell monitor die 700 can beintegrated in the top cap of the battery cell 100 in one embodiment, orin the center of the battery cell 100 in another embodiment.

The battery pack 300 (400) can be used in many kinds of electronicsystems. FIG. 8 illustrates an electronic system 800, such as anelectronic vehicle, a computer, etc., in accordance with one embodimentof the present invention. In one embodiment, the electronic system 800can include a battery pack 804 and a load 806 coupled to the batterypack 804. In one embodiment, the load 806 can include, but is notlimited to, a vehicle motor, a computer system, etc. In one embodiment,the electronic system 800 includes an input terminal 802 that can becoupled to an adapter (not shown in FIG. 8 for purposes of brevity andclarity). The adapter can charge the battery pack 804 in a certaincondition. The battery pack 804 can supply power to the load 806. In oneembodiment, the battery pack 804 employs the configuration as shown inFIG. 3/FIG. 4. The battery pack 804 includes one or more battery cells,each of which is embedded with a cell monitor to monitor the batterycell. Therefore, the battery pack 804 can be monitored accurately and beprotected from any undesirable conditions of each battery cell thereof,in one embodiment.

FIG. 9 illustrates a flowchart 900 of operations performed by a batterysystem, in accordance with one embodiment of the present invention. Thebattery system can employ the configuration as shown in FIG. 3/FIG. 4,in one embodiment. FIG. 9 is described in combination with FIG. 1, FIG.2A, and FIG. 2B. In block 902, each battery cell in a battery pack ismonitored respectively by a corresponding cell monitor 101 and thus analert signal 191 indicative of a predetermined condition of theassociated battery cell can be generated. The cell monitor 101 isembedded in each battery cell. In one embodiment, a temperature sensor115 can monitor a temperature of the battery cell and thus the cellmonitor 101 generates the alert signal 191 if the temperature of thebattery cell is greater than a predetermined threshold. A voltage sensor111 can monitor a voltage of the battery cell and thus the cell monitor101 generates the alert signal 191 if the voltage of the battery cell isgreater than a predetermined threshold. In block 904, the cell monitor101 generates an alert signal 191 indicative of a predeterminedcondition of the battery cell. In one embodiment, the predeterminedcondition can be an undesirable condition (e.g., over-voltage and/orover-temperature condition). In block 906, a protection action (e.g.,terminate battery charging/discharging) can be triggered according tothe alert signal 191. In one embodiment, the battery cell can bedisconnected from a load or a charger in response to the alert signal.

Accordingly, a battery pack is provided in the present disclosure. Acell monitor is embedded in each battery cell of the battery pack formonitoring the corresponding battery cell. When an undesirable condition(e.g., over-temperature condition and/or over-voltage condition) isdetected in a battery cell, the corresponding cell monitor can generatean alert signal to the battery pack. A receiver in the battery pack canreceive the alert signal and generate a driving signal to a batterymanagement unit. The battery management unit can take correspondingaction to protect the battery pack from being deteriorated in theundesirable condition, e.g., disabling connection between the batterypack and other circuitry.

As disclosed hereinabove, each battery cell in a battery pack includes acell monitor for monitoring a corresponding battery cell individually.Once an undesirable condition is detected by a cell monitor in thecorresponding battery cell, the battery pack can be notified about theundesirable condition. Thus, the cell monitoring can be relativelyaccurate and the speed of responding to the undesirable condition can berelatively quick.

The embodiments that have been described herein, however, are some ofthe several that utilize this invention and are set forth here by way ofillustration but not of limitation. It is obvious that many otherembodiments, which will be readily apparent to those skilled in the art,may be made without departing materially from the spirit and scope ofthe invention as defined in the appended claims. Furthermore, althoughelements of the invention may be described or claimed in the singular,the plural is contemplated unless limitation to the singular isexplicitly stated.

1. A battery pack comprising: a battery cell; and a cell monitorembedded in said battery cell and operable for monitoring said batterycell and for generating an alert signal indicative of a predeterminedcondition of said battery cell.
 2. The battery pack of claim 1, whereinsaid cell monitor comprises a temperature sensor operable for monitoringa temperature of said battery cell, and wherein said cell monitorgenerates said alert signal if said temperature of said battery cell isgreater than a predetermined threshold.
 3. The battery pack of claim 1,wherein said cell monitor comprises a voltage sensor operable formonitoring a voltage of said battery cell, and wherein said cell monitorgenerates said alert signal if said voltage of said battery cell isgreater than a predetermined threshold.
 4. The battery pack of claim 1,wherein said cell monitor comprises: a sensing circuit operable fordetecting said predetermined condition of said battery cell and forgenerating a detecting signal; and a transmitter operable for receivingsaid detecting signal and for generating said alert signal according tosaid detecting signal from said sensing circuit.
 5. The battery pack ofclaim 4, wherein said transmitter comprises: a pulse generator operablefor receiving said detecting signal and for generating a plurality ofpulses according to said detecting signal; and a switch coupled to saidpulse generator and operable for receiving said plurality of pulses andfor generating said alert signal.
 6. The battery pack of claim 4,wherein said transmitter comprises: an oscillator operable for receivingsaid detecting signal and for generating said alert signal according tosaid detecting signal; and a capacitor coupled to said oscillator andoperable for transferring said alert signal to said battery cell.
 7. Thebattery pack of claim 1, further comprising: a receiver coupled to apositive terminal and a negative terminal of said batter pack andoperable for receiving said alert signal and for generating a drivingsignal according to said alert signal; and a battery management unitoperable for receiving said driving signal from said receiver and forgenerating a switching signal according to said driving signal, whereinsaid switching signal triggers a protection action for said batterypack.
 8. The battery -pack of claim 7, wherein said receiver comprises ahigh-pass filter.
 9. The battery pack of claim 7, wherein said receivercomprises a band-pass filter.
 10. The battery pack of claim 7, whereinsaid battery management unit comprises: a rectifier for receiving saiddriving signal and for generating a voltage signal; and a comparator forcomparing said voltage signal with a reference signal, wherein saidswitching signal is generated according to a result of said comparison.11. An electronic system comprising: a load; and a battery pack operablefor supplying power to said load, wherein said battery pack comprises: abattery cell; and a cell monitor embedded in said battery cell, andoperable for monitoring said battery cell and for generating an alertsignal indicative of a predetermined condition of said battery cell. 12.The electronic system of claim 11, wherein said cell monitor comprises atemperature sensor operable for monitoring a temperature of said batterycell, and wherein said cell monitor generates said alert signal if saidtemperature of said battery cell is greater than a predeterminedthreshold.
 13. The electronic system of claim 11, wherein said cellmonitor comprises a voltage sensor operable for monitoring a voltage ofsaid battery cell, and wherein said cell monitor generates said alertsignal if said voltage of said battery cell is greater than apredetermined threshold.
 14. The electronic system of claim 11, whereinsaid cell monitor comprises: a sensing circuit operable for detectingsaid predetermined condition of said battery cell and for generating adetecting signal; and a transmitter operable for receiving saiddetecting signal and for generating said alert signal according to saiddetecting signal from said sensing circuit.
 15. The electronic system ofclaim 14, wherein said transmitter comprises: a pulse generator operablefor receiving said detecting signal and for generating a plurality ofpulses according to said detecting signal; and a switch coupled to saidpulse generator and operable for receiving said plurality of pulses andfor generating said alert signal.
 16. The electronic system of claim 14,wherein said transmitter comprises: an oscillator operable for receivingsaid detecting signal and for generating said alert signal according tosaid detecting signal; and a capacitor coupled to said oscillator andoperable for transferring said alert signal to said battery cell. 17.The electronic system of claim 11, further comprising: a receivercoupled to a positive terminal and a negative terminal of said batterpack and operable for receiving said alert signal and for generating adriving signal according to said alert signal; and a battery managementunit operable for receiving said driving signal and for generating aswitching signal according to said driving signal, wherein saidswitching signal triggers a protection action for said battery pack. 18.The electronic system of claim 17, wherein said battery management unitcomprises: a rectifier for receiving said driving signal and forgenerating a voltage signal; and a comparator for comparing said voltagesignal with a reference signal.
 19. The electronic system of claim 11,where said load comprises a vehicle motor.
 20. The electronic system ofclaim 11, wherein said load comprises a computer system.
 21. A methodfor monitoring a battery pack, comprising: monitoring a battery cell insaid battery pack by a cell monitor which is embedded in said batterycell; and generating an alert signal indicative of a predeterminedcondition of said battery cell.
 22. The method of claim 21, comprising:monitoring a temperature of said battery cell; and generating said alertsignal if said temperature of said battery cell is greater than apredetermined threshold.
 23. The method of claim 21, comprising:monitoring a voltage of said battery cell; and generating said alertsignal if said voltage of said battery cell is greater than apredetermined threshold.
 24. The method of claim 21, comprising:triggering a protection action for said battery pack according to saidalert signal.